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[X86] Move '0-x == y --> x+y == 0' and similar combines to EmitCmp. 

AArch64 handles this pattern in their lowering code. By emitting
CMN. ARM handles it as an isel pattern.
This commit is contained in:
Craig Topper 2020-02-16 22:13:11 -08:00
parent 28213680b2
commit b62de210cf
1 changed files with 18 additions and 15 deletions
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33
llvm/lib/Target/X86/X86ISelLowering.cpp
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@ -21209,6 +21209,24 @@ static SDValue EmitCmp(SDValue Op0, SDValue Op1, unsigned X86CC,
Op1 = DAG.getNode(ISD::TRUNCATE, dl, CmpVT, Op1);
}
// 0-x == y --> x+y == 0
// 0-x != y --> x+y != 0
if (Op0.getOpcode() == ISD::SUB && isNullConstant(Op0.getOperand(0)) &&
(X86CC == X86::COND_E || X86CC == X86::COND_NE)) {
SDVTList VTs = DAG.getVTList(CmpVT, MVT::i32);
SDValue Add = DAG.getNode(X86ISD::ADD, dl, VTs, Op0.getOperand(1), Op1);
return Add.getValue(1);
}
// x == 0-y --> x+y == 0
// x != 0-y --> x+y != 0
if (Op1.getOpcode() == ISD::SUB && isNullConstant(Op1.getOperand(0)) &&
(X86CC == X86::COND_E || X86CC == X86::COND_NE)) {
SDVTList VTs = DAG.getVTList(CmpVT, MVT::i32);
SDValue Add = DAG.getNode(X86ISD::ADD, dl, VTs, Op0, Op1.getOperand(1));
return Add.getValue(1);
}
// Use SUB instead of CMP to enable CSE between SUB and CMP.
SDVTList VTs = DAG.getVTList(CmpVT, MVT::i32);
SDValue Sub = DAG.getNode(X86ISD::SUB, dl, VTs, Op0, Op1);
@ -44523,21 +44541,6 @@ static SDValue combineSetCC(SDNode *N, SelectionDAG &DAG,
SDLoc DL(N);
if (CC == ISD::SETNE || CC == ISD::SETEQ) {
// 0-x == y --> x+y == 0
// 0-x != y --> x+y != 0
if (LHS.getOpcode() == ISD::SUB && isNullConstant(LHS.getOperand(0)) &&
LHS.hasOneUse()) {
SDValue Add = DAG.getNode(ISD::ADD, DL, OpVT, RHS, LHS.getOperand(1));
return DAG.getSetCC(DL, VT, Add, DAG.getConstant(0, DL, OpVT), CC);
}
// x == 0-y --> x+y == 0
// x != 0-y --> x+y != 0
if (RHS.getOpcode() == ISD::SUB && isNullConstant(RHS.getOperand(0)) &&
RHS.hasOneUse()) {
SDValue Add = DAG.getNode(ISD::ADD, DL, OpVT, LHS, RHS.getOperand(1));
return DAG.getSetCC(DL, VT, Add, DAG.getConstant(0, DL, OpVT), CC);
}
if (SDValue V = combineVectorSizedSetCCEquality(N, DAG, Subtarget))
return V;
}